Increasing regulatory and operational pressure has resulted in the need for hydrocarbons that have low sulfur levels and nitrogen levels. Hydrotreating processes are used by petroleum refiners to remove heteroatoms, such as sulfur and nitrogen, from hydrocarbon streams such as naphtha, kerosene, diesel, gas oil, vacuum gas oil (VGO), and reduced crude.
Hydrotreating is generally accomplished by contacting a hydrocarbon feedstock in a hydrotreating reaction vessel, or zone, with a suitable hydrotreating catalyst under hydrotreating conditions of elevated temperature and pressure in the presence of a hydrogen-containing treat gas to yield a product having the desired level of sulfur and/or nitrogen.
Conventional hydrotreating catalysts generally contain a Group VIB metal with one or more Group VIII metals as promoters on a refractory support, such as alumina. Hydrotreating catalysts that are particularly suitable for hydrodesulfurization (HDS), as well as hydrodenitrogenation (HDN), generally contain molybdenum or tungsten on alumina promoted with a metal such as cobalt, nickel, iron, or a combination thereof. Cobalt promoted molybdenum on alumina catalysts are most widely used when the limiting specifications are hydrodesulfurization, while nickel promoted molybdenum on alumina catalysts are the most widely used for hydrodenitrogenation, partial aromatic saturation, as well as hydrodesulfurization.
There is a continuing need for ever-more reactive and effective catalysts for removing heteroatoms, such as nitrogen and sulfur from hydrocarbon streams.